By 1985, the perpetual calendar had spent a decade as a relic in the world of watchmaking, but Patek brought it thundering back into the spotlight with the introduction of the 3940. The model was noted for its slim case, ultra-thin automatic movement, and three registers laid out with the perfect proportions that almost no one has improved on since. However, many people seem to forget that the brand launched a second reference alongside it. The 3945 is essentially the same watch with the lugs removed and an integrated gold bracelet taking their place. Undeservedly, the 3945 has lived in its fraternal twin's shadow ever since.